/*
 * Copyright (c) 2014, KJFrameForAndroid 张涛 (kymjs123@gmail.com).
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.kymjs.aframe.core;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Factory and utility methods for {@link Executor}, {@link ExecutorService},
 * {@link ScheduledExecutorService}, {@link ThreadFactory}, and {@link Callable}
 * classes defined in this package. This class supports the following kinds of
 * methods:
 * 
 * <ul>
 * <li>Methods that create and return an {@link ExecutorService} set up with
 * commonly useful configuration settings.
 * <li>Methods that create and return a {@link ScheduledExecutorService} set up
 * with commonly useful configuration settings.
 * <li>Methods that create and return a "wrapped" ExecutorService, that disables
 * reconfiguration by making implementation-specific methods inaccessible.
 * <li>Methods that create and return a {@link ThreadFactory} that sets newly
 * created threads to a known state.
 * <li>Methods that create and return a {@link Callable} out of other
 * closure-like forms, so they can be used in execution methods requiring
 * <tt>Callable</tt>.
 * </ul>
 * 
 * @since 1.5
 * @author Doug Lea
 * 
 */

/**
 * 线程池管理类:本类摘自jdk1.8中的
 * java.util.concurrent.Executors，用于替代原org.kymjs.aframe.ThreadPoolManager类
 * 并做了适当修改，使其更适合于手机运行<br>
 * <b>创建时间</b> 2014-8-14
 * 
 * @author Doug Lea
 * @author kymjs(kymjs123@gmail.com)
 * @version 1.1
 */
public class KJThreadExecutors {

    /**
     * Creates a thread pool that reuses a fixed number of threads operating off
     * a shared unbounded queue. At any point, at most <tt>nThreads</tt> threads
     * will be active processing tasks. If additional tasks are submitted when
     * all threads are active, they will wait in the queue until a thread is
     * available. If any thread terminates due to a failure during execution
     * prior to shutdown, a new one will take its place if needed to execute
     * subsequent tasks. The threads in the pool will exist until it is
     * explicitly {@link ExecutorService#shutdown shutdown}.
     * 
     * @param nThreads
     *            the number of threads in the pool
     * @return the newly created thread pool
     * @throws IllegalArgumentException
     *             if {@code nThreads <= 0}
     */
    public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads, 0L,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<Runnable>());
    }

    /**
     * Creates a thread pool that reuses a fixed number of threads operating off
     * a shared unbounded queue, using the provided ThreadFactory to create new
     * threads when needed. At any point, at most <tt>nThreads</tt> threads will
     * be active processing tasks. If additional tasks are submitted when all
     * threads are active, they will wait in the queue until a thread is
     * available. If any thread terminates due to a failure during execution
     * prior to shutdown, a new one will take its place if needed to execute
     * subsequent tasks. The threads in the pool will exist until it is
     * explicitly {@link ExecutorService#shutdown shutdown}.
     * 
     * @param nThreads
     *            the number of threads in the pool
     * @param threadFactory
     *            the factory to use when creating new threads
     * @return the newly created thread pool
     * @throws NullPointerException
     *             if threadFactory is null
     * @throws IllegalArgumentException
     *             if {@code nThreads <= 0}
     */
    public static ExecutorService newFixedThreadPool(int nThreads,
            ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(nThreads, nThreads, 0L,
                TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<Runnable>(), threadFactory);
    }

    /**
     * Creates an Executor that uses a single worker thread operating off an
     * unbounded queue. (Note however that if this single thread terminates due
     * to a failure during execution prior to shutdown, a new one will take its
     * place if needed to execute subsequent tasks.) Tasks are guaranteed to
     * execute sequentially, and no more than one task will be active at any
     * given time. Unlike the otherwise equivalent
     * <tt>newFixedThreadPool(1)</tt> the returned executor is guaranteed not to
     * be reconfigurable to use additional threads.
     * 
     * @return the newly created single-threaded Executor
     */
    public static ExecutorService newSingleThreadExecutor() {
        return new FinalizableDelegatedExecutorService(
                new ThreadPoolExecutor(1, 1, 0L,
                        TimeUnit.MILLISECONDS,
                        new LinkedBlockingQueue<Runnable>()));
    }

    /**
     * Creates an Executor that uses a single worker thread operating off an
     * unbounded queue, and uses the provided ThreadFactory to create a new
     * thread when needed. Unlike the otherwise equivalent
     * <tt>newFixedThreadPool(1, threadFactory)</tt> the returned executor is
     * guaranteed not to be reconfigurable to use additional threads.
     * 
     * @param threadFactory
     *            the factory to use when creating new threads
     * 
     * @return the newly created single-threaded Executor
     * @throws NullPointerException
     *             if threadFactory is null
     */
    public static ExecutorService newSingleThreadExecutor(
            ThreadFactory threadFactory) {
        return new FinalizableDelegatedExecutorService(
                new ThreadPoolExecutor(1, 1, 0L,
                        TimeUnit.MILLISECONDS,
                        new LinkedBlockingQueue<Runnable>(),
                        threadFactory));
    }

    /**
     * Creates a thread pool that creates new threads as needed, but will reuse
     * previously constructed threads when they are available. These pools will
     * typically improve the performance of programs that execute many
     * short-lived asynchronous tasks. Calls to <tt>execute</tt> will reuse
     * previously constructed threads if available. If no existing thread is
     * available, a new thread will be created and added to the pool. Threads
     * that have not been used for sixty seconds are terminated and removed from
     * the cache. Thus, a pool that remains idle for long enough will not
     * consume any resources. Note that pools with similar properties but
     * different details (for example, timeout parameters) may be created using
     * {@link ThreadPoolExecutor} constructors.
     * 
     * @return the newly created thread pool
     */
    public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L,
                TimeUnit.SECONDS, new SynchronousQueue<Runnable>());
    }

    /**
     * Creates a thread pool that creates new threads as needed, but will reuse
     * previously constructed threads when they are available, and uses the
     * provided ThreadFactory to create new threads when needed.
     * 
     * @param threadFactory
     *            the factory to use when creating new threads
     * @return the newly created thread pool
     * @throws NullPointerException
     *             if threadFactory is null
     */
    public static ExecutorService newCachedThreadPool(
            ThreadFactory threadFactory) {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L,
                TimeUnit.SECONDS, new SynchronousQueue<Runnable>(),
                threadFactory);
    }

    /**
     * Creates a single-threaded executor that can schedule commands to run
     * after a given delay, or to execute periodically. (Note however that if
     * this single thread terminates due to a failure during execution prior to
     * shutdown, a new one will take its place if needed to execute subsequent
     * tasks.) Tasks are guaranteed to execute sequentially, and no more than
     * one task will be active at any given time. Unlike the otherwise
     * equivalent <tt>newScheduledThreadPool(1)</tt> the returned executor is
     * guaranteed not to be reconfigurable to use additional threads.
     * 
     * @return the newly created scheduled executor
     */
    public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
        return new DelegatedScheduledExecutorService(
                new ScheduledThreadPoolExecutor(1));
    }

    /**
     * Creates a single-threaded executor that can schedule commands to run
     * after a given delay, or to execute periodically. (Note however that if
     * this single thread terminates due to a failure during execution prior to
     * shutdown, a new one will take its place if needed to execute subsequent
     * tasks.) Tasks are guaranteed to execute sequentially, and no more than
     * one task will be active at any given time. Unlike the otherwise
     * equivalent <tt>newScheduledThreadPool(1, threadFactory)</tt> the returned
     * executor is guaranteed not to be reconfigurable to use additional
     * threads.
     * 
     * @param threadFactory
     *            the factory to use when creating new threads
     * @return a newly created scheduled executor
     * @throws NullPointerException
     *             if threadFactory is null
     */
    public static ScheduledExecutorService newSingleThreadScheduledExecutor(
            ThreadFactory threadFactory) {
        return new DelegatedScheduledExecutorService(
                new ScheduledThreadPoolExecutor(1, threadFactory));
    }

    /**
     * Creates a thread pool that can schedule commands to run after a given
     * delay, or to execute periodically.
     * 
     * @param corePoolSize
     *            the number of threads to keep in the pool, even if they are
     *            idle.
     * @return a newly created scheduled thread pool
     * @throws IllegalArgumentException
     *             if {@code corePoolSize < 0}
     */
    public static ScheduledExecutorService newScheduledThreadPool(
            int corePoolSize) {
        return new ScheduledThreadPoolExecutor(corePoolSize);
    }

    /**
     * Creates a thread pool that can schedule commands to run after a given
     * delay, or to execute periodically.
     * 
     * @param corePoolSize
     *            the number of threads to keep in the pool, even if they are
     *            idle.
     * @param threadFactory
     *            the factory to use when the executor creates a new thread.
     * @return a newly created scheduled thread pool
     * @throws IllegalArgumentException
     *             if {@code corePoolSize < 0}
     * @throws NullPointerException
     *             if threadFactory is null
     */
    public static ScheduledExecutorService newScheduledThreadPool(
            int corePoolSize, ThreadFactory threadFactory) {
        return new ScheduledThreadPoolExecutor(corePoolSize,
                threadFactory);
    }

    /**
     * Returns an object that delegates all defined {@link ExecutorService}
     * methods to the given executor, but not any other methods that might
     * otherwise be accessible using casts. This provides a way to safely
     * "freeze" configuration and disallow tuning of a given concrete
     * implementation.
     * 
     * @param executor
     *            the underlying implementation
     * @return an <tt>ExecutorService</tt> instance
     * @throws NullPointerException
     *             if executor null
     */
    public static ExecutorService unconfigurableExecutorService(
            ExecutorService executor) {
        if (executor == null) {
            throw new NullPointerException();
        }
        return new DelegatedExecutorService(executor);
    }

    /**
     * Returns an object that delegates all defined
     * {@link ScheduledExecutorService} methods to the given executor, but not
     * any other methods that might otherwise be accessible using casts. This
     * provides a way to safely "freeze" configuration and disallow tuning of a
     * given concrete implementation.
     * 
     * @param executor
     *            the underlying implementation
     * @return a <tt>ScheduledExecutorService</tt> instance
     * @throws NullPointerException
     *             if executor null
     */
    public static ScheduledExecutorService unconfigurableScheduledExecutorService(
            ScheduledExecutorService executor) {
        if (executor == null) {
            throw new NullPointerException();
        }
        return new DelegatedScheduledExecutorService(executor);
    }

    /**
     * Returns a default thread factory used to create new threads. This factory
     * creates all new threads used by an Executor in the same
     * {@link ThreadGroup}. Each new thread is created as a non-daemon thread
     * with priority set to the smaller of <tt>Thread.NORM_PRIORITY</tt> and the
     * maximum priority permitted in the thread group. New threads have names
     * accessible via {@link Thread#getName} of <em>pool-N-thread-M</em>, where
     * <em>N</em> is the sequence number of this factory, and <em>M</em> is the
     * sequence number of the thread created by this factory.
     * 
     * @return a thread factory
     */
    public static ThreadFactory defaultThreadFactory() {
        return new DefaultThreadFactory();
    }

    /**
     * Legacy security code; do not use.
     */
    public static ThreadFactory privilegedThreadFactory() {
        return new PrivilegedThreadFactory();
    }

    /**
     * Returns a {@link Callable} object that, when called, runs the given task
     * and returns the given result. This can be useful when applying methods
     * requiring a <tt>Callable</tt> to an otherwise resultless action.
     * 
     * @param task
     *            the task to run
     * @param result
     *            the result to return
     * @return a callable object
     * @throws NullPointerException
     *             if task null
     */
    public static <T> Callable<T> callable(Runnable task, T result) {
        if (task == null) {
            throw new NullPointerException();
        }
        return new RunnableAdapter<T>(task, result);
    }

    /**
     * Returns a {@link Callable} object that, when called, runs the given task
     * and returns <tt>null</tt>.
     * 
     * @param task
     *            the task to run
     * @return a callable object
     * @throws NullPointerException
     *             if task null
     */
    public static Callable<Object> callable(Runnable task) {
        if (task == null) {
            throw new NullPointerException();
        }
        return new RunnableAdapter<Object>(task, null);
    }

    /**
     * Returns a {@link Callable} object that, when called, runs the given
     * privileged action and returns its result.
     * 
     * @param action
     *            the privileged action to run
     * @return a callable object
     * @throws NullPointerException
     *             if action null
     */
    public static Callable<Object> callable(
            final PrivilegedAction<?> action) {
        if (action == null) {
            throw new NullPointerException();
        }
        return new Callable<Object>() {
            public Object call() {
                return action.run();
            }
        };
    }

    /**
     * Returns a {@link Callable} object that, when called, runs the given
     * privileged exception action and returns its result.
     * 
     * @param action
     *            the privileged exception action to run
     * @return a callable object
     * @throws NullPointerException
     *             if action null
     */
    public static Callable<Object> callable(
            final PrivilegedExceptionAction<?> action) {
        if (action == null) {
            throw new NullPointerException();
        }
        return new Callable<Object>() {
            public Object call() throws Exception {
                return action.run();
            }
        };
    }

    /**
     * Legacy security code; do not use.
     */
    public static <T> Callable<T> privilegedCallable(
            Callable<T> callable) {
        if (callable == null) {
            throw new NullPointerException();
        }
        return new PrivilegedCallable<T>(callable);
    }

    /**
     * Returns a {@link Callable} object that will, when called, execute the
     * given <tt>callable</tt> under the current with the current context class
     * loader as the context class loader.
     * 
     * @return a callable object
     * @throws NullPointerException
     *             if callable null
     */
    public static <T> Callable<T> privilegedCallableUsingCurrentClassLoader(
            Callable<T> callable) {
        if (callable == null) {
            throw new NullPointerException();
        }
        return new PrivilegedCallableUsingCurrentClassLoader<T>(
                callable);
    }

    // Non-public classes supporting the public methods

    /**
     * A callable that runs given task and returns given result
     */
    static final class RunnableAdapter<T> implements Callable<T> {
        final Runnable task;
        final T result;

        RunnableAdapter(Runnable task, T result) {
            this.task = task;
            this.result = result;
        }

        public T call() {
            task.run();
            return result;
        }
    }

    /**
     * A callable that runs under established access control settings
     */
    static final class PrivilegedCallable<T> implements Callable<T> {
        private final Callable<T> task;
        private final AccessControlContext acc;

        PrivilegedCallable(Callable<T> task) {
            this.task = task;
            this.acc = AccessController.getContext();
        }

        public T call() throws Exception {
            try {
                return AccessController.doPrivileged(
                        new PrivilegedExceptionAction<T>() {
                            public T run() throws Exception {
                                return task.call();
                            }
                        }, acc);
            } catch (PrivilegedActionException e) {
                throw e.getException();
            }
        }
    }

    /**
     * A callable that runs under established access control settings and
     * current ClassLoader
     */
    static final class PrivilegedCallableUsingCurrentClassLoader<T>
            implements Callable<T> {
        private final Callable<T> task;
        private final AccessControlContext acc;
        private final ClassLoader ccl;

        PrivilegedCallableUsingCurrentClassLoader(Callable<T> task) {
            // BEGIN android-removed
            // SecurityManager sm = System.getSecurityManager();
            // if (sm != null) {
            // // Calls to getContextClassLoader from this class
            // // never trigger a security check, but we check
            // // whether our callers have this permission anyways.
            // sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
            //
            // // Whether setContextClassLoader turns out to be necessary
            // // or not, we fail fast if permission is not available.
            // sm.checkPermission(new
            // RuntimePermission("setContextClassLoader"));
            // }
            // END android-removed
            this.task = task;
            this.acc = AccessController.getContext();
            this.ccl = Thread.currentThread().getContextClassLoader();
        }

        public T call() throws Exception {
            try {
                return AccessController.doPrivileged(
                        new PrivilegedExceptionAction<T>() {
                            public T run() throws Exception {
                                ClassLoader savedcl = null;
                                Thread t = Thread.currentThread();
                                try {
                                    ClassLoader cl = t
                                            .getContextClassLoader();
                                    if (ccl != cl) {
                                        t.setContextClassLoader(ccl);
                                        savedcl = cl;
                                    }
                                    return task.call();
                                } finally {
                                    if (savedcl != null)
                                        t.setContextClassLoader(savedcl);
                                }
                            }
                        }, acc);
            } catch (PrivilegedActionException e) {
                throw e.getException();
            }
        }
    }

    /**
     * The default thread factory
     */
    static class DefaultThreadFactory implements ThreadFactory {
        private static final AtomicInteger poolNumber = new AtomicInteger(
                1);
        private final ThreadGroup group;
        private final AtomicInteger threadNumber = new AtomicInteger(
                1);
        private final String namePrefix;

        DefaultThreadFactory() {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() : Thread
                    .currentThread().getThreadGroup();
            namePrefix = "pool-" + poolNumber.getAndIncrement()
                    + "-thread-";
        }

        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r, namePrefix
                    + threadNumber.getAndIncrement(), 0);
            if (t.isDaemon()) {
                t.setDaemon(false);
            }
            if (t.getPriority() != Thread.NORM_PRIORITY) {
                t.setPriority(Thread.NORM_PRIORITY);
            }
            return t;
        }
    }

    /**
     * Thread factory capturing access control context and class loader
     */
    static class PrivilegedThreadFactory extends DefaultThreadFactory {
        private final AccessControlContext acc;
        private final ClassLoader ccl;

        PrivilegedThreadFactory() {
            super();
            // BEGIN android-removed
            // SecurityManager sm = System.getSecurityManager();
            // if (sm != null) {
            // // Calls to getContextClassLoader from this class
            // // never trigger a security check, but we check
            // // whether our callers have this permission anyways.
            // sm.checkPermission(SecurityConstants.GET_CLASSLOADER_PERMISSION);
            //
            // // Fail fast
            // sm.checkPermission(new
            // RuntimePermission("setContextClassLoader"));
            // }
            // END android-removed
            this.acc = AccessController.getContext();
            this.ccl = Thread.currentThread().getContextClassLoader();
        }

        public Thread newThread(final Runnable r) {
            return super.newThread(new Runnable() {
                public void run() {
                    AccessController.doPrivileged(
                            new PrivilegedAction<Void>() {
                                public Void run() {
                                    Thread.currentThread()
                                            .setContextClassLoader(
                                                    ccl);
                                    r.run();
                                    return null;
                                }
                            }, acc);
                }
            });
        }
    }

    /**
     * A wrapper class that exposes only the ExecutorService methods of an
     * ExecutorService implementation.
     */
    static class DelegatedExecutorService extends
            AbstractExecutorService {
        private final ExecutorService e;

        DelegatedExecutorService(ExecutorService executor) {
            e = executor;
        }

        public void execute(Runnable command) {
            e.execute(command);
        }

        public void shutdown() {
            e.shutdown();
        }

        public List<Runnable> shutdownNow() {
            return e.shutdownNow();
        }

        public boolean isShutdown() {
            return e.isShutdown();
        }

        public boolean isTerminated() {
            return e.isTerminated();
        }

        public boolean awaitTermination(long timeout, TimeUnit unit)
                throws InterruptedException {
            return e.awaitTermination(timeout, unit);
        }

        public Future<?> submit(Runnable task) {
            return e.submit(task);
        }

        public <T> Future<T> submit(Callable<T> task) {
            return e.submit(task);
        }

        public <T> Future<T> submit(Runnable task, T result) {
            return e.submit(task, result);
        }

        public <T> List<Future<T>> invokeAll(
                Collection<? extends Callable<T>> tasks)
                throws InterruptedException {
            return e.invokeAll(tasks);
        }

        public <T> List<Future<T>> invokeAll(
                Collection<? extends Callable<T>> tasks,
                long timeout, TimeUnit unit)
                throws InterruptedException {
            return e.invokeAll(tasks, timeout, unit);
        }

        public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
                throws InterruptedException, ExecutionException {
            return e.invokeAny(tasks);
        }

        public <T> T invokeAny(
                Collection<? extends Callable<T>> tasks,
                long timeout, TimeUnit unit)
                throws InterruptedException, ExecutionException,
                TimeoutException {
            return e.invokeAny(tasks, timeout, unit);
        }
    }

    static class FinalizableDelegatedExecutorService extends
            DelegatedExecutorService {
        FinalizableDelegatedExecutorService(ExecutorService executor) {
            super(executor);
        }

        protected void finalize() {
            super.shutdown();
        }
    }

    /**
     * A wrapper class that exposes only the ScheduledExecutorService methods of
     * a ScheduledExecutorService implementation.
     */
    static class DelegatedScheduledExecutorService extends
            DelegatedExecutorService implements
            ScheduledExecutorService {
        private final ScheduledExecutorService e;

        DelegatedScheduledExecutorService(
                ScheduledExecutorService executor) {
            super(executor);
            e = executor;
        }

        public ScheduledFuture<?> schedule(Runnable command,
                long delay, TimeUnit unit) {
            return e.schedule(command, delay, unit);
        }

        public <V> ScheduledFuture<V> schedule(Callable<V> callable,
                long delay, TimeUnit unit) {
            return e.schedule(callable, delay, unit);
        }

        public ScheduledFuture<?> scheduleAtFixedRate(
                Runnable command, long initialDelay, long period,
                TimeUnit unit) {
            return e.scheduleAtFixedRate(command, initialDelay,
                    period, unit);
        }

        public ScheduledFuture<?> scheduleWithFixedDelay(
                Runnable command, long initialDelay, long delay,
                TimeUnit unit) {
            return e.scheduleWithFixedDelay(command, initialDelay,
                    delay, unit);
        }
    }

    /** Cannot instantiate. */
    private KJThreadExecutors() {}
}
